In recent years, battery systems equipped with a large number of cells such as a power storage device for a vehicle, a power storage device for stabilization associated with a system, a power storage device for emergency have attracted attention. In order to achieve the performance of these systems, it is necessary to calculate parameters such as a charging rate (SOC) or a deterioration rate (SOH) of each cell and a maximum rechargeable current (allowable charge/discharge current) and to appropriately equalize the charging rates of the cells. In order to achieve the above purpose, a circuit (cell controller) for cell voltage measurement is attached to each cell, and a battery controller equipped with a central processing unit (CPU) performs the above calculation or operations on the basis of information transmitted from the cell controllers. However, there is a problem in that, as the number of cells included in the battery system is increased, the number of communication lines connecting the cell controllers and a battery controller is increased, and a production cost required for connection of the lines is also increased.
In order to solve the problem, by using power line communication (“power line communication circuit of modifying voltage detection signals detected by a voltage detection circuit into power line communication signals and superposing the modified power line communication signals between positive and negative output terminals to output the superposed, modified power line communication signal”) disclosed in, for example, PTL 1, communication between the cell controllers and the battery controller can be implemented without separately preparing a communication line.